Effect of cooling temperature on the performance of a solar adsorption chiller with the enhanced mass transfer

Abstract

Nowadays, the renewable and sustainable solar adsorption cooling technology has attracted extensive attention. Enhancing the mass transfer is a main method to improve the performance of a solar adsorption chiller, which can significantly increase the desorption of refrigerant. However, the desorbed refrigerant is high-temperature vapor, which usually cannot be condensed into liquid in time, so that the adsorbent bed pressure would be increased and the desorption process would be slower. This paper proposes a new enhanced mass transfer mode with two condensers and a micro vacuum pump for decreasing the desorption pressure further. In the new system, the refrigerant vapor is condensed before being pumped into the receiver, which can increase the density of refrigerant and improve the mass flow rate with the same pressure and working speed of pump. A solar adsorption cooling system with activated carbon-methanol working pair was designed and constructed. The performance of the solar adsorption cooling system with enhanced model was evaluated and compared with three different cooling temperatures of 20 °C, 30 °C, and 40 °C, respectively. The results show that reducing the cooling temperature can greatly improve the coefficient of performance (COP) under the mode of enhanced mass transfer, but the cavitation phenomenon also will be caused in the micro vacuum pump when the cooling temperature is lower than 30 °C. With a cooling temperature of 20 °C, the average desorption pressure was 21.86 kPa, and the COP of the system was 0.169.